Brush, in Particular Toothbrush, and Method of Manufacturing the Same

ABSTRACT

The present invention provides a brush including a brush head (28) carrying bristle filaments (6), a brush neck and a handle stem, which are arranged one behind the other in the longitudinal direction of the brush, in which a bristle carrier (32) holding the bristle filaments (6) is formed from a hard component (16) and the handle stem is formed from a foamed plastic material (24). In a method according to the invention, a first plastic component (16) is injected into a first mold cavity (14) to form a bristle carrier (32) holding bristle filaments (6), the bristle carrier (32) is transferred to a further mold cavity (22) and, in a further molding cycle, a foaming plastic (24) is introduced into the further mold cavity (22), which foams in the further mold cavity (22).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the United States national phase of International Application No. PCT/EP2020/058741 filed Mar. 27, 2020, and claims priority to German Patent Application No. 10 2019 204 397.6 filed Mar. 28, 2019, the disclosures of each of which are hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a brush, in particular a toothbrush, and a method of manufacturing the same.

Description of Related Art

A brush, in particular a toothbrush, has a brush body carrying bristle filaments. The brush body has a brush head with the bristle filaments being attached thereto, a handle stem for handling the brush, and a brush neck located therebetween.

Such brushes in the form of toothbrushes have been known for a long time.

EP 1 110 478 A1 originating from to the applicant relates to a method of manufacturing a toothbrush. In this process, an injection mold is first fitted with multiple bristle bundles, each consisting of a plurality of bristle filaments. The bristle bundles are first melted on the attachment side so that a thickening is formed there. This thickening is overmolded with a first plastic component in a first injection mold. The intermediate product is then transferred to a further, larger injection mold and overmolded with a second plastic component.

Using the process the production of visually appealing brushes should be possible. This is because the overmolding of the attachment-side ends of the bristle filaments can usually only be carried out with a limited injection pressure, since the bristle filaments protrude through the mold cavity formed for the overmolding. For this purpose, a hole-shaped channel is formed in the injection mold to hold the respective bristle bundle. Complete tightness is, however, not achieved at this point. Thus, upon overmolding the thickening and the attachment-side end of the bristle bundle a reduced injection pressure has to be applied, which, however, results in a surface of the intermediate product molded in this way that does not always meet the visual and design requirements to be placed on a hygiene product such as a toothbrush. Thus, the intermediate product is overmolded with another plastic component in the second mold cavity. The second mold cavity is thereby sealed by surfaces of the intermediate product formed by the first plastic component, thereby allowing higher injection pressures to act in the second mold cavity.

The present invention is intended to provide a brush and a method of manufacturing the same which permits more efficient use of the plastic material employed. This is intended to allow a more cost-effective manufacturing of brushes of the type discussed above, in particular toothbrushes.

SUMMARY OF THE INVENTION

To solve this problem, the present invention proposes a brush having the features disclosed herein.

This brush may be a toothbrush comprising, in a manner known per se, a brush head, a brush neck and a handle stem, the brush neck being provided between the brush head and the handle stem. These components are arranged one behind the other in the longitudinal direction of the toothbrush. They typically form the brush body of the toothbrush, which is an elongated brush body. According to the present invention, a bristle carrier of the brush holding the bristle elements is formed of a hard component. This hard component is a common plastic material capable of holding the bristle filaments, a plurality of bristle filaments regularly combined into a bristle bundle, to the brush head with the necessary pull-out strength. The filaments may be held without anchors in the manner described above. For this purpose, the bristle filaments are embedded in the hard component forming the bristle carrier during formation of the bristle carrier. The filaments may, however, also be fixed with an anchor. In this process, the bristle carrier is first produced, usually by injection molding, and then, usually after the brush body is completely finished, the bristle filaments are attached to the brush head.

In the brush according to the present invention, the brush head may have several bristle carriers. In this case, the bristle carriers are configured as fastening elements for fastening the bristle filaments. Individual bristle carriers, each carrying at least one bristle filament or a bristle bundle, may be hingedly connected to another bristle carrier. The bristle carriers may be connected to one another via film hinges, so that all the bristle carriers of the brush head may be formed in a uniform injection molding cycle.

The brush according to the present invention has a handle stem formed from a foamed plastic. The foamed plastic may also form the brush neck. The foamed plastic allows a brush body to be produced in the usual and previously known dimensions, but using a reduced amount of plastic. The foaming results in improved use of the amount of plastic material introduced during injection molding to form the brush body. In total, the brush is lighter. It may be manufactured at a lower cost because a reduced weight of plastic has to be used to form the brush body without sacrificing the dimensional design of the brush.

From DE 100 34 839 A1 originating from the applicant it is known that in order to manufacture a thick-walled handle stem of a toothbrush, this handle stem is overmolded several times with a low-cost recyclate, so that the handle stem is formed by several ring-like layers around a core of a high-quality virgin plastic component. Such a design cannot be economically produced in the field of toothbrushes, since available recyclate regularly contains unspecified ingredients and additives, so that the recyclate does not meet the requirements for chemical purity of sanitary articles (FDA conformity).

The bristle carrier is preferably configured as a bristle carrier restricted to the brush head. The handle stem and the brush neck are formed from the foamed plastic. The connection may be made, for example, according to EP 3 087 864 A1.

The foamed plastic may also form parts of the brush head. In the case of multiple bristle carriers provided in the area of the brush head, the foamed plastic may connect them with each other or surround them. As a result, the brush head, too, is formed into an aesthetically pleasing segment of the brush body by the outer enclosure with the foamed plastic, albeit with reduced plastic weight.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and advantages of the present invention will be apparent from the following description of embodiments of a schematic method in conjunction with the drawing. In this drawing:

FIG. 1 shows a schematic sectional view illustrating a first injection molding step for producing the brush head;

FIG. 2 shows a representation according to FIG. 1 for illustrating the second injection molding step;

FIG. 3 shows a representation according to FIG. 2 for an alternative embodiment;

FIG. 4 shows a schematic sectional view illustrating a first injection molding step for manufacturing a brush head according to an alternative embodiment;

FIG. 5 shows a representation according to FIG. 4 illustrating the second injection molding step for manufacturing the second embodiment example;

FIG. 6 shows a schematic sectional view illustrating the embodiment of the second embodiment of a brush head;

FIG. 7 shows a schematic sectional view illustrating the attachment of a bristle filament according to a first embodiment; and

FIG. 8 shows a schematic sectional view illustrating the attachment of a bristle filament according to a second variant.

DETAILED DESCRIPTION

In a preferred further embodiment of the present invention, the bristle carrier is therefore at least partially surrounded by the foamed plastic.

According to a preferred further embodiment of the present invention, the brush head, the handle stem and the brush neck consist of the foamed plastic and the hard component. In other words, the brush according to the present invention is preferably formed solely by the brush body formed from these two components and the cleaning elements attached thereto. These cleaning elements may be bristle filaments or soft elastic cleaning elements, for example made of a TPE. The restriction to the use of only two plastic materials forming the brush body simplifies manufacture and increases economy.

In a preferred variant of the present invention, the foamed plastic has essentially the same hardness as the hard component. Preferably, the hardness, in particular the tensile strength, of the foamed plastic is at least 50%, preferably at least 80%, of that of the hard component. In this way, it is possible to produce a sufficiently stable handle stem while at the same time reducing the amount of material used.

In a further variant of the present invention, the foamed plastic is sufficiently compressible in itself so that the brush provides a pleasant haptic feel. In this case, haptic elements formed from a separate material on the outer surface, in particular of the handle stem, may be dispensed with. Overmolding of the brush body with a soft elastic plastic compound, as is known from the prior art for forming haptic elements, may be omitted.

A hard component within the meaning of the present invention is, in particular, an engineering plastic such as PA, PE or PP. With regard to the desired pull-out strength of the bristle filaments with respect to the brush body, the hard component has a tensile strength of preferably at least 80 MPa, particularly preferably at least 90 MPa, most preferably at least 500 MPa.

The portion of the brush body formed by the foamed plastic is preferably shaped as an integral foam. With regard to hygienic requirements, the foamed plastic forms a closed thick outer skin, so that even those surface areas of the brush body which are made of the foamed plastic cannot absorb moisture and pick up dirt. The core of the foamed material, on the other hand, has a cellular structure, with the density of the foamed material usually decreasing from the outside to the inside. Such an integral foam may be the result of mechanical or physical foaming. Equally well, the foamed plastic may be formed by chemical foaming.

Insofar as the foamed plastic extends into the brush head, the embodiment should be such that the bristle filaments project through and away from an upper outer surface of the brush head formed by the hard component, whereas adjacent to this projected-through outer surface and in the same plane or extension thereof, the surface is formed by the foamed plastic. This is usually achieved by the foamed plastic circumferentially surrounding the upper outer surface. When viewing the upper surface of the brush head, the hard component may then be recognized in the area of the bristle filaments and the foamed plastic may be recognized where no bristle elements are provided. This embodiment offers further functional advantages. For example, the foamed plastic in the area of the brush head may realize a softness that serves as mucous membrane protection when the brush is used as a toothbrush in the oral cavity. This allows a synergistic effect to be utilized. On the one hand, material for forming the brush body is saved; on the other hand, functional areas on the brush head are formed by the foamed plastic.

The same applies to technical functional elements of the brush head, such as joints, which are to be formed or shaped between individual bristle carriers. Due to the reduced rigidity of the foamed plastic compared with a conventional hard component, relative pivoting of bristle carriers relative to one another on the brush body may be easily achieved.

By arranging the foamed plastic on a rear surface of the brush head opposite the upper outer surface, a tongue scraper may be formed there from the foamed plastic. Also in this case, the inherent compressibility of the foamed plastic, which is preferably present, permits a corresponding functionality by means of which mucous membranes within the oral cavity may be effectively treated and which a conventional hard component does not provide.

Insofar as the rear surface is formed entirely from the foamed plastic, corresponding functional elements may be provided over a large area on the rear surface. This may also result in comprehensive impact protection for the sensitive oral mucous membranes, as the bristle carrier(s) formed from the hard component is/are almost completely encapsulated. In this embodiment only the surface directly penetrated by the bristle filaments, which cannot come into contact with the mucous membranes of the mouth due to the spacing by the bristle filaments, is formed from the hard component.

To increase the usability of the brush according to the present invention, it is proposed according to a preferred further embodiment of the present invention to provide the foamed plastic on the rear surface of the brush head in such a way that at least one functional surface formed by the hard component is surrounded circumferentially by the foamed plastic. The functional surface may, for example, have ribs or nubs, which are formed by the hard component and accordingly have a higher mechanical effectiveness with respect to the surface to be cleaned.

The connection between the hard component and the solidified foamed plastic material of the brush head may be material-locking and/or form-fitting. A form-fit connection is created in particular by the solidified foamed plastic sealing the hard component completely or at least almost completely into itself. In the case of almost complete sealing, only surface regions of the upper outer surface of the brush head circumferentially surrounding the bristle filaments are formed by the hard component. For example, each individual bristle bundle may be circumferentially surrounded by a ring of the hard component, which forms an annular surface on the upper outer surface, but which is otherwise formed by the foamed plastic. In this case, the surface segments of the brush head usually merge into one another without shoulders or seams, so that contamination and bacteria cannot settle on the brush head.

Individual support rings or a uniform grid of rings produced by injection molding with connecting webs provided between them as film hinges may also be realized as bristle carriers, each individual ring usually carrying a single bristle bundle. The bristle bundle may be fixed in a ring closed on the underside conventionally with an anchor, by means of adhesive or welded joints. A ring as a bristle carrier may also be open on the underside, so that the bristle bundle protrudes through the ring and is held positively on the ring surface opposite the upper outer surface via a thickening formed on the bristle bundle and secured to the bristle carrier element with good pull-out strength.

With regard to the method aspect of the underlying problem, the present invention proposes a method of manufacturing a brush, wherein a first plastic component is injected into a first mold cavity to form a bristle carrier and then the intermediate product thus produced is transferred into a further mold cavity that is regularly larger than the first mold cavity and, in a further molding cycle, a foaming plastic is introduced into the further mold cavity. This foaming plastic is foamed in the further mold cavity, resulting in a form-fitting and/or material-fitting connection between the hard component forming the bristle carrier and the solidified foamed plastic.

FIGS. 1 and 2 illustrate two successive steps in the two-component injection molding of a brush body not shown in greater detail, which is configured as the brush body of a toothbrush and has a brush head shown in section in the Figures, a brush neck adjoining it in the longitudinal direction and a handle stem adjoining the brush neck.

During manufacture, a perforated field plate 2 is first tamped with at least one bristle bundle 4. For this purpose, bristle filaments 6 forming the bristle bundle 4 are pushed through a hole 8 and melted on at the end to form a thickening 10. The perforated field plate 2 is connected to an injection mold half 12 a to form a first mold nest 14 together with an injection mold half 12 b. A hard component 16 is injected into this first mold nest 14 as the first plastic component.

After solidification of the hard component 16, an intermediate product marked with reference character 18 in FIG. 1 is ejected. Ejection takes place together with the perforated field plate 2, which is placed in a sealing manner against a second injection mold half 20 a, which forms a second mold cavity 22 with a further second injection mold half 20 b and the perforated field plate 2. A foaming plastic 24 is introduced into this second mold nest 22, which is caused to foam or is foamed physically and/or chemically and/or mechanically. Preferably, an integral foam is formed so that the foamed plastic 24 solidifies with a closed thicker outer skin against the perforated field plate 2 surrounding the second mold nest 22 and the second injection mold halves 20 a, 20 b, but has a density that decreases towards the interior.

In this context, it should be understood that FIGS. 1 and 2 merely schematically illustrate the section through a brush according to the invention. It is understood that, with respect to the desired fastening of the bristle bundles 4, the hard component 16 is be formed appropriately strongly around the thickening 10, but on the other hand, with respect to the desired saving of material, as predominant a part as possible of the brush body to be produced is to be formed by the foamed plastic 24.

FIG. 3 shows an example of an embodiment modified with respect to FIGS. 1 and 2 after injection of the foamed plastic 24. Identical components are marked with the same reference signs. The second embodiment according to FIG. 3 differs above all in that an upper outer surface of the brush head 28 shown in cross-section, which is penetrated by the bristle bundles 4 and is marked with reference sign 26, is formed quite predominantly by the foamed plastic 24. Only an exemplary circular ring surface 30 circumferentially surrounds the bristle bundle 4, which in this case has a circular cross-section.

Accordingly, the surface regions of the brush head 28 penetrated by the bristle bundles 4 are formed by the hard component 16, but the upper outer surface 26 is otherwise predominantly formed by the foamed plastic 24. The variant shown also leads to a completely form-fitting sealing of the bristle carrier formed by the hard component 16 and identified by reference sign 32.

FIGS. 4 to 6 illustrate the manufacturing of a second embodiment of a bristle carrier identified by reference numeral 32 in FIG. 6, which has a hard component identified by reference numeral 16 forming a core within the bristle carrier 32. This hard component 16 is produced in a first mold cavity 14 as shown in FIG. 4. As in FIG. 2, the mold cavity 14 is enclosed by two injection mold halves 12 a, 12 b and a pin plate 34 which carries a pin 36 which projects into the first mold cavity 14.

FIG. 4 illustrates the embodiment after injection of the hard component 16 enclosing the pin 36.

According to FIG. 5, this intermediate product 18 is transferred by displacing the pin plate 34 into the second mold cavity 22, which is dimensioned such that a free space remains between the outer surface of the intermediate product 18 and the mold cavity surfaces of the second mold cavity 22. In the present case, this free space is formed to surround the hard component 16 in the shape of a trough. Now, as in the first embodiment, foamed plastic 24 is introduced into the second mold cavity 22. The foamed plastic solidifies to form a skin, which solidifies against the surfaces bounding the second mold cavity 22. Thus, the surface penetrated by the pin 36, hereinafter referred to as the surface of the brush head 28, also exhibits a sealed surface configuration.

After ejecting the bristle carrier 32, the pin plate 34 is also removed. Instead of the pin 36, the bristle carrier 32 now has a blind hole boring 38.

As FIG. 7 illustrates, a bristle bundle 4 may be driven into the blind hole boring 38 via a conventional anchor 40 and fastened therein.

Compared with this first variant, FIG. 8 shows a second variant, in which the bristle bundle 4 has a thickening 10 formed by melting, which is introduced into the blind hole boring 38 that is shorter in this case. An annular region of the surface surrounding the blind hole boring 38 is then plastically deformed so that the material initially bounding the cylindrical blind hole boring 38 on the surface of the bristle carrier 32 is displaced radially in the direction of the bristle bundle 4 and the thickening 10 is held positively in the blind hole boring 38.

In one embodiment, for example, by relative movement of the pin 36, the intermediate product 18 may also be spaced from the pin plate 34 so that the core formed by the hard component 16 is essentially fully sealed by the foamed plastic 24.

In this regard, a single core formed by the hard component 16 may be provided to each individual bristle bundle 4. The core may also be formed by a ring, through which the bristle bundle protrudes, but which is otherwise accommodated within the foamed plastic 24, the bristle bundle 4 being positively fixed relative to the ring by the thickening 10 on the rear side facing away from the front surface of the bristle carrier 32.

The fastening of the bristle bundle 4 formed by the hard component 16 may accordingly have various specific embodiments.

LIST OF REFERENCE SIGNS

2 perforated field plate

4 bristle bundle

6 filament

8 hole

10 thickening

12 a first injection mold half

12 b first injection mold half

14 first mold cavity

16 hard component

18 intermediate product

20 a second injection mold half

20 b second injection mold half

22 second mold cavity

24 foamed plastic

26 upper outer surface

28 brush head

30 ring surface

32 bristle carrier

34 pin plate

36 pin

38 blind hole boring

40 anchor 

1. A toothbrush, comprising a brush head carrying bristle filaments, a brush neck and a handle stem, which are arranged one behind the other in the longitudinal direction of the brush, wherein a bristle carrier holding the bristle filaments is formed of a hard component and the handle stem is formed of a foamed plastic.
 2. The toothbrush according to claim 1, wherein the bristle carrier is formed as a bristle carrier element restricting itself to the brush head, and in that the handle stem and the brush neck are formed from the foamed plastic.
 3. The toothbrush according to claim 2, wherein the bristle carrier is at least partially surrounded by the foamed plastic.
 4. The toothbrush according to claim 1, wherein the brush head, the handle stem and the brush neck consist of the foamed plastic and the hard component.
 5. The toothbrush according to claim 1, wherein the brush head has a plurality of bristle carrier elements connected to one another by the foamed plastic.
 6. The toothbrush according to claim 1, wherein the bristle filaments project from an upper outer surface of the brush head formed by the hard component and are surrounded circumferentially by the foamed plastic.
 7. The toothbrush according to claim 6, wherein the foamed plastic is provided on a rear surface of the brush head provided opposite to the upper outer surface.
 8. The toothbrush according to claim 7, the rear surface is formed of the foamed plastic.
 9. The toothbrush according to claim 8, wherein the foamed plastic circumferentially surrounds a functional surface formed by the hard component and exposed at the rear surface.
 10. The toothbrush according to claim 1, wherein the hard component has a tensile strength of at least 500 MPa.
 11. A method of manufacturing a toothbrush comprising a brush head provided with bristle filaments, a handle stem and a brush neck located therebetween, by injection molding, wherein a first plastic component is injected into a first mold cavity to form a bristle carrier holding bristle filaments, wherein the bristle carrier is transferred into a further mold cavity and in a further molding cycle a foaming plastic is introduced into the further mold cavity, which foams in the further mold cavity.
 12. The method according to claim 11, wherein the bristle filaments are embedded in the first plastic component when forming the bristle carrier.
 13. The method according to claim 11, wherein after ejecting the bristle carrier the bristle filaments are fixed to the bristle carrier.
 14. The method according to claim 11, wherein the bristle carrier is formed as a bristle carrier element restricting itself to the brush head, and in that the handle stem and the brush neck are formed from the foaming plastic.
 15. The method according to claim 11, wherein the foaming plastic is physically or mechanically foamed. 